The composition of a bulk material can be analyzed based on the characteristics of the gamma rays detected by a gamma ray detector. For example, elements typically emit gamma rays at certain characteristic energies when activated with a suitable source of neutrons during neutron activation. These techniques have been used to analyze bulk materials, for example, to determine the sulfur content of coal using gamma ray detection during neutron activation.
High sulfur levels in coal are generally bad for the environment. The sulfur content of coal may be analyzed by detecting gamma rays emitted from sulfur during neutron activation. The sulfur content of coal may be used to comply with environmental regulations. Bulk material analyzers generally include a fast neutron source and a radiation detector spaced apart from the source. The fast neutrons originating from the source collide with elements in the bulk material. The neutrons may collide with elements with small nuclei, such as hydrogen or carbon, and be slowed by elastic scattering, or these collisions can result in the emission of inelastic gamma rays, which subsequently can result in the slowing down of the neutrons. Upon slowing down, the neutrons may be captured with higher probability and another set of gamma rays may be emitted. The resulting gamma rays, either before or after neutron slowing, are detected by the radiation detectors and the resulting spectra are analyzed to obtain information about the elemental amounts in the bulk material.